linux-kernel - Re: [PATCH 1/7] KVM: MMU: optimize pte write path if don't have protected sp

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Message-ID: <4DCF8CBC.1040602@redhat.com>
Date:	Sun, 15 May 2011 11:20:12 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 1/7] KVM: MMU: optimize pte write path if don't have protected
 sp

On 05/15/2011 12:35 AM, Xiao Guangrong wrote:
> Simply return from kvm_mmu_pte_write path if no shadow page is
> write-protected, then we can avoid to walk all shadow pages and hold
> mmu-lock
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 2841805..971e2d2 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -498,6 +498,7 @@ static void account_shadowed(struct kvm *kvm, gfn_t gfn)
>   		linfo = lpage_info_slot(gfn, slot, i);
>   		linfo->write_count += 1;
>   	}
> +	atomic_inc(&kvm->arch.indirect_shadow_pages);
>   }
>
>   static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
> @@ -513,6 +514,7 @@ static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
>   		linfo->write_count -= 1;
>   		WARN_ON(linfo->write_count<  0);
>   	}
> +	atomic_dec(&kvm->arch.indirect_shadow_pages);
>   }

These atomic ops are always called from within the spinlock, so we don't 
need an atomic_t here.

Sorry, I should have noticed this on the first version.





-- 
error compiling committee.c: too many arguments to function

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